tang vs black rockweed

tang and black rockweed both are nouns.

Word	Noun	Adjective	Verb	Adverb
tang	Yes	No	No	No
black rockweed	Yes	No	No	No

As nouns, tang and black rockweed are synonyms defined as:

tang and black rockweed: a common rockweed used in preparing kelp and as manure

Other synonyms of tang include bladder fucus, bladderwrack, Fucus vesiculosus.

tang (noun)	black rockweed (noun)
any of various kelps especially of the genus Laminaria	a common rockweed used in preparing kelp and as manure
any of various coarse seaweeds
brown algae seaweed with serrated edges
a common rockweed used in preparing kelp and as manure
a tart spicy quality
the taste experience when a savoury condiment is taken into the mouth